Reading at night is very important for me. With REB 1100 I had a great night reading, so I spent some time to find the best solution for my new Sony 500.
1. I started with $5 NextTech LED lamp (rechargable Ni-Cd, RadioShack). Light is good, but intensity changes fast with discharging; not very uniform illumination and image is too contrast.
2. Flexible LED (similar to recommended by Sony). $10 at Barnes and Nobles. 2x2032. Better than 1), but the same too contrast image and necessity to change the batteries.
Strange enough, but manufactures do not care about adjustment of light intensity. To me this is important because light should be adjusted to illumination conditions, besides spectrum gets more "warm" with lowing the intensity. So I desided improve the lamp. First, I installed charge-pump LED driver (FAN5607, Fairchild, ~1.5$ at DigiKey )which gives constant (and adjustable) intensity independent on battery voltage; second, I replaced 2032 batteries to rechargable Li-ion (from GameBoy console).
Inside the lamp cap there are 2 LED, 4 capacitors, 1 chip and potentiometer with the switch. The Li-ion battery is in the box at the bottom of the lamp.
Gets much better, the intensity can be changed for more convinient reading.
3) Next approach. I purchased LightWedge backlight ($25, Barnes and Nobles,
http://www.lightwedge.com/prod_paperback.html). The light is more "scattered" and gives much more comfortable reading (though the illumination is not very uniform). The bad things are:
i) The wedge does not fit the reader size ii) it requires 4 AAA battaries (to heavy) 3) light is not stabilized and adjustable.
So I modified the LightWedge the following way:
1) Cut the wedge to fit the reader screen
2) Made a hole to get 2 LED according to new size
2) made the box with Li-ion rechargable battery with the FAN5607 chip, potentiometer and the switch.
Here are the images:
The illumination is not very uniform, but reading is much more comfortable than with any of other sources. Almost that comfortable as with REB 1100 (b/w LCD with back illumination)
May be my experience will be useful.
Mikhail